Section 4.1 Speed & Velocity b What is motion? A change in the position of an object relative to another object (a reference point), which is assumed to be at rest. Uniform motion is when an object moves in a straight line at constant speed. b We describe an object’s motion by talking about its... Speed – how quickly something moves.

b How would you try to calculate the speed of a moving object? Speed = distance object moves time it takes to move there Section 4.1 Speed & Velocity speed (v) = d (distance) t (time)

b The units for speed are distance units over time units. What units are commonly used to describe distance and time? : Section 4.1 Speed & Velocity

b Average Speed: When you divide the total distance of the trip by the total time taken. Section 4.1 Speed & Velocity

b Instantaneous speed: The actual speed an object has at any given moment. What is an example of a device that gives instantaneous speed? – –Car speedometer Section 4.1 Speed & Velocity

b Velocity (v): Speed WITH direction. Velocity is a vector. Vector – a variable that has magnitude (or a number) and a direction. Section 4.1 Speed & Velocity +65 m/s -65 mph

So … What’s The Difference? b b Speed or Velocity?: 1) Johnny drove to work travelling 75 mph east. ~ VeLoCiTy 2) Alicia walks 5 mph every day to get to her middle school. ~ SpEeD Section 4.1 Speed & Velocity

b Solving Problems With Speed: How far do you go if you drive for 2 hours at a speed of 100 km/h? Looking for?Looking for?... Distance Given?Given? … speed = 100 km/h time = 2 h Section 4.1 Speed & Velocity Relationships? Relationships? d = v x t Solution? Solution? d = 100 km/h x 2 h = 200 km = 200 km